Process of treating the surface of granite or like stone



Patented Nov. 23, 1926.

UNITE STATES PATENT OFFEQE.

ELROY A. CHASE, OF NORTHFIELD, VERMONT.

PROCESS OF TREATING THE SURFACE OF GRANITE OR LIKE STONE.

No Drawing.

This invention relates to a process of treating the surface of granite or like stone, by which process new and very desirable results are obtained.

It is custonary to use a sand blast for treating the surface of granite and particularly for producing letters and other designs thereon, the sand blast being commonly directed through a stencil, so that the back ground is cut away by the sand blast belew the original surface of the stone. In the cutting of such materials and particularly of light colored granite, it has been found 7 very difficult to bring out a satisfactory contrast between the natural or unpolished surface of the stone and the surface produced by the sand blast, particularly when sinking a design therein.

It is the object of my invention to provide a process of treating the surface of granite and like stone by which the portions subjected to the sand blast will acquire a different finish and appearance, so that the contrast with the remaining surface of the work will be more marked and the design will stand out more prominently therefrom.

The detailed steps of my improved process are hereinafter described and will be more specifically set forth in the appended claims.

In carrying out my improved process, I make use of an abrasive compound comprising a mixture of fine grains of sand with a certain proportion of fine grains of a hard abrasive material, such as carborundum or silicon carbide.

The proportions of the mixture may be somewhat widely varied, an increased amount of the abrasive material producing more rapid cutting of the stone but at the same time increasing the cost of the mixture. The most desirable proportion to be used on a given piece of work depends upon a careful consideration and comparison of the cost of the mixture with the cost of the time and labor consumed in cutting the design.

I find that a very effective mixture con sists of about one part of silicon carbide or carborundum and about one part of sand. The sand may be an artificial product having sharp or crystalline grains with a marked cutting action of its own, or it may consist of a fine sea sand in which the grains are small and rounded rather than crystalline. The artificial sand produces somewhat more Serial No. 47,158.

hen this abrasive mixture is used in' cutting granite or like stone with a sand blast, I have found that the surface produced is distinctly and prominently darker in appearance and color than the surface produced by the use of sand alone. This darker color is not the result of discoloration or stain due to the carborundum or carbide, but appears to be caused by the abrasive action of the carborundum upon the stone, in addition to the usual action of the sand. The surfaces appear to be somewhat more smoothly finished and to have a cer tain degree of polish which is not found where sand alone is used as an abrasive.

lVhile my improved process is particularly adapted for sinking a design below a previously finished surface of stone, it is also well adapted for finishing fiat or irreg- 'ular surfaces of stone and when thus used the finished stone is substantially darker in appearance than that produced by the usual sand blast with sand alone.

Vhile I have used carborundum and silicon carbide as convenient terms for designating the abrasive to be mixed with the sand, it will be understood that other abrasives having similar characteristics ma be substituted for use in my improved process and that their'use comes within the scope of my invention as set forth in the claims.

Having fully described the steps of my improved process and the results and advantages thereof, I do not Wish to be otherwise limited to the details herein disclosed but what I claim is 1. The process of treating the surface of granite or like stone which consists in sand blasting the stone with a mixture of fine grains of sand and fine grains of silicon car- 3. The process of treating the surface ol granite or like stone which consists in sand lasting the stone with a mixture of a rela tively large portion of small rounded grains of sand and a substantially smaller portion of fine grains of a hard abrasive polishing material.

4. The process of treating the surface of granite or like stone which consists in subjecting the surface, of the stone to the simultaneous action of sea sand. and not more than an equal portion of fine grains of hard abrasive directed as: a sand blast against the surface of said stone.

5. The process of producing the ellect of contrasting colors in granite or like stone, which consists in sand blasting part of the surface with a mixture of sand and fine grains of silicon carbide.

In testimony whereof I have hereunto affixed my signature.

ELROY A, onasn 

